基于超声的组织弹性测量之剪切波传播法

Soft Tissue Elasticity by Ultrasound-based Measurement of Shear Wave Propagation

近年来,随着临床实践上肝脏硬度检测的广泛开展,软组织弹性的测量也受到广大科研和医护人员的重视。除了弹性的直接测量法(印压和压缩测试)外,剪切波传播测量法也是一种实用的间接测量组织弹性的方法,如在肝脏硬度检测里面广泛使用的瞬时弹性测量技术,就是利用剪切波的传播速度方法来测量肝脏组织的弹性。该方法的原理是根据剪切波在组织里面的传播速度与组织剪切模量的理论关系,利用测得的剪切波的传播速度来计算组织的弹性系数。在组织中产生剪切波的方法有很多种,常用的包括外振动器振动法和声辐射力振动法。振动的形式也可以分为连续性振动或脉冲振动。超声是一种常用的探测振动传播的方法,其B模成像功能还可以用来引导测试的感兴趣区域,增加探测的准确性。本文主要介绍利用超声对剪切波传播进行测量,然后获取传播参数用以计算组织弹性的方法。首先介绍测量的原理和各种相关技术,然后介绍这些方法在组织弹性测量中一些热门的应用,最后对该领域存在的不足和对未来的发展前景进行总结和展望。

With the fast development of the liver stiffness measurement clinically in recent years, the measurement of soft tissue elasticity has attracted broad attentions from R＆D engineers to clinicians. In addition to the direct methods such as indentation and compression, the measurement of shear wave propagation is another common indirect approach used to obtain the soft tissue elasticity. For example, it has been used in the transient elastography, a technique currently widely used to measure the liver stiffness. The shear wave propagation method utilizes the measurement of propagation speed of the shear wave to extract the tissue elasticity, which is based on a theoretical relalionship between propagation speed and shear modulus of the tested material. A number of methods can be adopted to induce the shear wave in soft tissues, including external mechanical vibration using a vibrator and internal vibration by acoustic radiation force. The vibration can also he induced in a continuous or pulsed form. Ultrasound is a common modality to detect the propagation of shear wave in soft tissue, and B-mode uhrasmmd imaging can be used to guide the selection of region of interest for detection, which improves the accuracy of measurement. This paper mainly introduees the techniques related to the use of ultrasound for detection of shear wave propagation in order for the tissue elasticity measurement. Firstly we introduce the measurement prineiple and various techniques, then we describe some active areas of applications for these techniques, and finally we summarize some problems remained in this field and look forward to some future perspectives in solving these problems.